With quick development of Data Service, Data Network tends to be integrated with conventional Time Division Multiplexing (TDM) Network. Multi-Service Transport Platform (MSTP) equipments are the key equipments for network integration, and these kinds of equipments have gone through three generations: Ethernet transparent transmission, Ethernet Layer 2 (L2) Switch and embedded Multiple Protocol Label Switch (MPLS) and Resilient Packet Ring (RPR). For the sake of inter-operation of these MSTP equipments, it is necessary to realize inter-operation of the data, the network management messages and the control messages transmitted by MSTP.
Generally, in SDH network, Generic Framing Procedure (GFP) Protocol is used to encapsulate the data transferring messages, such as Ethernet messages, etc. However, the network management messages and the control messages are transmitted in SDH network by encapsulating these messages into SDH DCC (D1-D12) bytes. As for the network management messages based on Open System Interconnection (OSI), they are usually encapsulated into SDH DCC via LAPD (the control protocol of Data Link Layer As for the network management messages or the control messages based on IP (Internet Protocol), they can be encapsulated into SDH DCC via LAPD, or the IP signals can be encapsulated into Ethernet, and then transmitted out of band, or the IP signals that have been encapsulated into Ethernet can be encapsulated into SDH DCC via LAPS (Link Access Protocols or GFP and like and then transmitted in band.
Like DCC in SDH network, overhead in the OTN network are used otherwise, payload in PDH network is used.
When LAPD is used to transmit the network management messages or the control messages, the working process is as follows: at a source, when upper layer data arrive, the specific beginning characters as flags are added to them, then whether the same characters as the specific characters acting as flags exist in the data is judged, if yes, the specific characters are transformed, and then the data are transmitted after the filling bytes are added and FCS (Frame Check Sequence) is performed. At a sink, the specific characters are judged, the beginning of the frame is determined, the messages are received, then the specific characters in the data are inverse-transformed, the filling bytes are removed, and the messages are received and sent to upper layer for further processing.
If LAPD is used, since specific characters are used as flags, it is necessary to fill characters and to process the specific characters appeared in the encapsulated data, which results in that, however, it is impossible to realize inter-operation of the network management messages and the control messages between the equipments of different manufacturers. Moreover, since specific frame delimiting bytes are needed in LAPD, it is necessary to perform the processing of filling redundant codes, which makes the processing complicated. Additionally, LAPD only supports the Point-to-Point topology, but does not support other topology.
On the other hand, if the IP signals are encapsulated into Ethernet and then transmitted out of band, or the IP signals encapsulated in the Ethernet are encapsulated into SDH DCC via the protocol such as LAPS or GFP and then transmitted in band, one more time of the encapsulating processing is needed, which makes the processing complicated.
In view of the above fact, the object of the present invention is to provide a simple method for sending and receiving the network management messages and/or the control messages between the equipments of different manufacturers in Synchronous Digital Hierarchy (SDH) network, Synchronous Optical Network (SONET), Optical Transmission Network (OTN) and Plesiochronous Digital Hierarchy (PDH) networks.